Field of the Invention
The present invention relates to an optical reading apparatus for reading an original document surface by optically scanning, and an image forming apparatus, carrying the optical reading apparatus thereon, with a printing function to receive print data from an electronic copying function and the outside, and the like.
With rapid development of recent electronic technologies and optical technologies, high-quality, multifunction and downsized optical reading apparatuses and image forming apparatuses have been provided.
In the optical reading apparatus, a scanning pitch has become more fine to optically read an original document surface precisely. As photoelectric conversion means for converting an optically read signal into an electric signal, a high resolution CCD sensor having more pixels is used. Further, the image forming apparatus (copying machine) carrying the optical reading apparatus has a facsimile function and a printer function to receive print data from an external data processing device such as a personal computer in addition to a copying function. Further, a function to transmit image data obtained by the optical reading apparatus to the data processing device such as a personal computer is required. As one image forming apparatus has these four functions, rationalization and downsizing of clerical work space is attained.
FIG. 1 shows a first example of the outer appearance of general conventional image forming apparatus having plural. The conventional image forming apparatus shown in FIG. 1 has paper trays for independently storing plural sizes of print sheets in a lower part of the cabinet, thus reducing the floor space. However, as discharge trays for holding discharged print sheets after image formation are protruded outward from the side surface side, the substantial floor space necessary for installation of the apparatus includes the discharge trays protruded outward from the side surface side.
FIG. 2 shows the outer appearance of “ABLE 3250” by Fuji Zerox Co., Ltd. To solve the above problem, the discharge tray is provided between a position under the housing of optical reading apparatus and a cabinet upper portion containing an image forming unit. In the image forming apparatus of this conventional art, as the discharge tray for storing print sheets after image formation is provided within the size of the cabinet without being protruded outward from the side surface side, the substantial floor space is greatly reduced.
FIG. 3 is a cross-sectional view of the optical reading apparatus of the conventional art in FIG. 2. An original document is placed on a platen glass 2 attached onto a chassis 1, and a first carriage 3 and a second carriage 7 in cooperation with each other project an image on the original document onto a photoelectric converting device (hereinbelow CCD) 12.
The placed original document is irradiated by a light source 4 provided in the first carriage 3. The diffused light of the emitted light passes through an opening 5 of the first carriage 3, and a first mirror 6 changes the optical path in a subscanning direction (direction of the original document movement). The optical-path changed image on the original document is changed downward by a second mirror 8 of the second carriage 7, and changed toward a lens 11 by a third mirror 9. The image light-gathered by the lens 11 is emitted on the CCD (photoelectric conversion device in the claims) 12 on a CCD board 13 fixed to the chassis 1 with an angle member 14. Note that in the present invention, the CCD is used as representative of the photoelectric conversion device, however, amorphous or MOS type photoelectric conversion device may be used.
The image converted by the CCD 12 into an electric signal is processed by an image processing circuit on a CCD board 13 and a control board (not shown) in the housing of the optical reading apparatus. The lens 11, the CCD board 13 and the control board are covered with a shielding plate 10 preventing entrance of unnecessarily diffused light from the light source 4.
The first carriage is subscanned at a speed twice faster than that of the second carriage such that the length of optical path from the original document surface through the three mirrors to the lens is always a fixed length.
Although not shown in the figure, the first carriage and the second carriage are supported by respectively different surfaces of guide rails. Further, a document scanning initial position of the first carriage and the second carriage is positioned at the right end of the platen glass 2, and the first carriage scans above the shielding plate 10 around the end of the subscanning. Accordingly, the thickness of the housing of the optical reading apparatus must be equal to or greater than the total amount of the thickness of the shielding plate and the thickness to the first carriage. Thus the thickness of the housing is limited by this amount. Further, space for holding the control board must be ensured in the housing.
In this manner, plural paper trays for various paper sizes are stacked in the lower part of the cabinet of the image forming apparatus, and the discharge tray is provided on an upper part of the cabinet. Further, as space for manual operation to pick up a sheet on the discharge tray is required above the discharge tray, the size of the cabinet of the image forming apparatus is large in height, and the optical reading apparatus set on the cabinet is provided in a very high position. Further, in many cases, an automatic document feeder (ADF) to pick up plural documents on the tray one by one and send them to the optical reading apparatus is also used. Thus, from the point of improvement in operability, it has been an important problem in the conventional image forming apparatus to reduce the height of the multifunction image formation apparatus.